Examining the influence of microclimate conditions on the breakup of surface-based temperature inversions in two proximal but dissimilar Yukon valleys

Abstract

Surface-based temperature inversions (SBIs) are frequent and strong in valleys of north-central Yukon, which drive annual average surface lapse rates that are strongly inverted (≤1.19°C 100 m⁻¹) within the first 100 to 150 vertical meters. This study aims to test the relationship of SBI breakup with local microclimate factors determining the influence on surface lapse rate breakup patterns. A field study was conducted using elevational transect analysis. SBI breakup in the non-winter season had a strong relationship between the diurnal cycle of increased solar radiation, warming of the surface, and development of atmospheric turbulence in the form of increased wind speed. SBIs during these non-winter seasons had a peak breakup time of 4 to 8 h following sunrise. Wintertime SBIs often persisted past the diurnal cycle and broke up independent of solar radiation, contributing significantly to the inverted average surface lapse rates. Mechanisms of SBI breakup during the winter are likely more synoptic in nature and one possible mechanism could be shallow cold air flows. Current classification of SBI duration as persistent or transient was reviewed and adjusted, and SBIs with a duration of 18 to 22 h were removed due to the breakup of those events being related to the diurnal cycle.